A chlorine-containing resin is a highly versatile resin, but it has a drawback of poor impact resistance. In particular, it is a great challenge of this resin to achieve both of the impact strength as well as other mechanical properties and the processability. So, a number of methods have been proposed in order to improve the impact resistance.
For example, it is disclosed that by blending particles of a silicone/acrylic composite rubber-based graft copolymer having a number average particle size of from 400 to 2000 nm and a proportion of the particles having a particle size of 300 nm or less in the entire particle size of 20% by volume or less into a chlorine-containing resin, the low temperature impact strength and high temperature mechanical properties are maintained and favorable processing characteristics, surface appearance of a molded product and coloring property may appear (Patent Document 1). However, there is a case in which the powder recovered by coagulation using a polyvalent metal salt as aggregating agent exhibits low dispersibility into a chlorine-containing resin compared to the powder recovered by spray and thus the resin does not sufficiently melt under usual molding conditions.
In order to improve this, for example, a rubbery polymer-containing material obtained by the spray recovery of a rubbery polymer containing a composite rubber composed of a polyorganosiloxane component and a polyalkyl(meth)acrylate component as a main component is disclosed (Patent Document 2). However, when the rubbery polymer-containing material is blended into a chlorine-containing resin, lubricity is imparted to the chlorine-containing resin to an excessive extent by the decomposition product of the emulsifier generated at the time of molding, thus the resin does not sufficiently melt under usual molding conditions, and as a result, a practically sufficient strength is not exerted in some cases.
As a technique to suppress the lubricity impartation by the decomposition product, for example, it is disclosed that the processability at the time of melt molding and impact resistance are improved without impairing the weather resistance by blending a graft copolymer (A) obtained by graft polymerizing a monomer mixture (a2) at from 0.1 to 50 parts by mass in the presence of an acrylic rubber (A1) at from 50 to 99.9 parts by mass [provided that the sum of (A1) and (a2) is 100 parts by mass] and in which the monomer mixture (a2) contains isobutyl methacrylate at from 1 to 99% by mass into a vinyl chloride resin (Patent Document 3). However, this technique is difficult to completely improve the lubricity imparted by the decomposition product derived from the emulsifier (surfactant) that is generated at the time of molding. In addition, the molded article thus obtained is also inferior in the low temperature impact strength required for a usual molded article.